Turbo Bypass

[Greg Hermann]

Steve--My reaction is that the throttles downstream of the turbos on the
road race motors were more in the interest of shutting down fast than
anything else--if you prang the car, you don't finish. But these cars are
so much quicker than anything we're talking about, I just don't think than
a half dozen engine revs would make much difference in a road car. Not to
say that you want a huge pressurized plenum.

You were looking in the right place for the lag on the Mustang. The carb.
If you have an intercooler, it gets worse. Think about what goes on if you
try to deal with wet flow through an intercooler. Basically, the fuel will
get in their and condense at inopportune times, and then come out all at
once at maybe even worse times. The squirt from the accelerator pumps takes
way too long to get to where it will do any good, even without an
intercooler.

                                        Regards, Greg

>Hmmm.  My '80's draw through turbo mustang (admittedly carbed) had tons of
>lag.  It was so bad that as soon as you finished braking for a corner you
>could go full throttle and get full boost on the corner exit.
>
>I know that Cosworth, Honda and I think Mercedes CART engines all use 9
>throttles currently.  1 per cylinder runner and 1 in front of the
>compressor.  In the turbo F1 days only renault and cosworth did it with 1
>throttle per bank and 1 in front of the compressor.  All the 4 cyl engines
>that had a single throttle in front of the compressor soon switched to 1 in
>front of the plenum due to driveability concerns.  The cosworth engines use
>a trick 4 bladed butterfly deal that gives the air a pre-swirl as it opens,
>but doesn't have a pressure drop across it.
>
>In addition, all of the turbo Group C and GTP cars used 1 throttle per bank
>without a byupass valve.
>
>Just my observations,
>
>Steve
>
>>yep.  Flashback: early 70's Accel marketed a kit that did it.  Overspeed at
>>part throttle/high load conditions.  But wow! the thing would hit (fast)
>with
>>big boost, when you stomped the pedal from a part throttle load.  The turbo
>>would be spinning at a bazillion rpm, in high vauumm,  and then the
>butterlfy
>>opens to feed it air..yeow!
>>Mike V.
>>